The fate of those onboard is not known.

A military helicopter carrying 19 passengers and four crew members has been missing in Laos since Monday and is said to have been in an accident. The fate of those onboard is not known.

Laos' defence ministry said on Tuesday that the helicopter was in an accident while flying to the Xiengkhuang and Houaphanh provinces and that it had lost communication shortly after it took off from the left Vientiane Capital.

Poor weather conditions hampered air search for the helicopter, the ministry said.

The MI-17 helicopter departed from the Wattay International Airport on Monday, but soon lost contact with air traffic control, and till 36 hours after it went missing, it was not clear if it was in an accident.

"We cannot confirm whether the aircraft has crashed or had to execute an emergency landing, because we have no proof at this time," an official had told Radio Free Asia on Tuesday.

The air tragedy comes a year after Lao Deputy Prime Minister Douangchay Phichit and several other officials were among the 17 killed when their military aircraft crashed near the Xiengkhuang airport on 17 May, last year, according to RFA.